/pages/<num> - one folder per page of the document; count from 1
/pages/<num>/fonts/<ID> - one folder per referenced font, e.g. 'TT0'
/pages/<num>/fonts/<ID>/Type - always 'Font'
/pages/<num>/fonts/<ID>/Subtype - e.g. 'TrueType'
/pages/<num>/fonts/<ID>/BaseFont - name of the font, e.g. 'Helvetica'
/pages/<num>/fonts/<ID>/FirstChar - ordinal of the first available glyph
/pages/<num>/fonts/<ID>/LastChar - ordinal of the last available glyph
/pages/<num>/layout.txt - raw PDF markup for a page
/pages/<num>/text/plain_text.txt - strings extracted from the page (rough!)
/pages/<num>/text/formatted_text.txt - very rough text rendering of the page
/pages/<num>/images/<num>.pdf - images used in the page, wrapped in a minimal PDF
/metadata/ - one file for every metadata key/value in the root dict
/metadata/ID - hexadecimal ID, hopefully unique
/metadata/Author - usually the author's username; depends on authoring tool
/metadata/Creator - name of generating application
/metadata/Producer - name of generating application
/metadata/CreationDate - e.g. D:20080104091746-06'00'
/metadata/ModDate - date last modified (usually the same as the CreationDate)
/filesystems/<name>/ - any embedded filesystems created by Fuse::PDF
/revisions/<num> - look at older versions of annotated PDFs

Return a list of one instance for each revision of the PDF. The first item on the list is this instance (the newest) and the last item on the list is the first revision of the PDF (the oldest). Unedited PDFs (the most common) will return just a one-element list.

If there is an older version of the PDF, extract that and return a new Fuse::PDF::ContentFS instance which applies to that revision. Multiple versions is feature supported by the PDF specification, so this action is consistent with other PDF revision editing tools.